CN113588931B - Top-down type pavement crack model based on indoor test and evaluation method thereof - Google Patents
Top-down type pavement crack model based on indoor test and evaluation method thereof Download PDFInfo
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Abstract
The invention provides a Top-down type pavement crack model based on an indoor test, which comprises a test box, wherein a temperature control device is arranged on the side surface of the test box, a circle of limiting plates are arranged in the test box, a road structure model with matched size is placed in a cavity formed by the limiting plates and a bottom plate of the test box, the road structure model comprises a soil base layer, a semi-rigid base layer and a surface layer which are sequentially arranged from bottom to Top, a height difference is gradually arranged from the middle of the semi-rigid base layer to one end of the semi-rigid base layer, a load instrument is arranged on the surface layer, connecting rods are connected to two sides of the test box, humidifying nozzles are arranged on the connecting rods and are connected with a humidifier, and the temperature control device, the humidifier and the load instrument are all connected with a power supply. The application also provides an evaluation method based on the crack model, provides evaluation indexes, can perform quantitative analysis on the formation of the crack and the existing repair method, and provides certain technical reference for the research and development of novel pavement materials and the selection of the crack repair method.
Description
Technical Field
The invention relates to the field of road detection, in particular to a Top-down type pavement crack model based on an indoor test and an evaluation method.
Background
At present, the high-grade highway in China basically adopts an asphalt pavement structure, and although the highway built by asphalt mixture has good pavement performance, various diseases can occur in short months and long 2-3 years after a vehicle is built, and particularly the problem of pavement cracks is the most serious. The initial pavement cracks are mostly Top-to-bottom pavement transverse seams or longitudinal seams (TDC) caused by the comprehensive effects of traffic load, environment, uneven roadbed height and the like, and the pavement mainly bears tensile stress and shear stress. In recent years, in the research of the United states, fatigue cracks related to load are mostly found on the surface of a pavement, and are expanded from top to bottom to become a main form of early-stage diseases of the asphalt pavement, so that the service life of the pavement basically does not reach the preset design age, and large-area maintenance is forced to be carried out, and the maintenance modes are various and have no uniform research scheme, thereby increasing a large amount of cost and being not beneficial to economic development.
At present, the research on TDC cracking mechanism of the asphalt pavement at home and abroad can be divided into a tensile cracking mode and a shear cracking mode, and the test methods mainly comprise an indirect tensile test, a direct tensile test, a bending tensile creep test and the like. Although the mechanical properties of the material are evaluated in a certain aspect by the test methods, the actual road surface condition is single, the actual stress condition of the road surface cannot be well reflected, and partial tests do not accord with the actual stress condition, so that the TDC cannot be well evaluated; on the other hand, the evaluation of the pavement crack repair method is more limited in indoor tests, and a uniform research scheme is not formed.
Therefore, the generation mechanism of the asphalt pavement TDC needs to be deeply researched, the quantitative analysis and the systematic evaluation of the generation and repair modes of the asphalt pavement TDC are carried out, and the method has important significance for the research and development of novel pavement materials and the selection of pavement maintenance modes.
Disclosure of Invention
The application provides a Top-down type pavement crack formation and repair evaluation model based on an indoor test, which simulates the actual stress condition of a road pavement, provides corresponding evaluation indexes, can perform quantitative analysis on crack formation and the existing repair method, and provides certain technical reference for research and development of novel pavement materials and selection of crack repair methods.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the utility model provides a Top-down type road surface crack forms and repairs evaluation model based on indoor test, includes the proof box, the side of proof box is equipped with temperature regulating device, be equipped with the round limiting plate in the proof box, the limiting plate with be used for placing big or small assorted road structure model in the cavity that the bottom plate of proof box formed, road structure model includes from following soil basic unit, semi-rigid basic unit and the surface course that sets gradually up, semi-rigid basic unit sets up the discrepancy in elevation gradually to one of them end from the centre, be equipped with the load appearance on the surface course, the both sides of proof box are connected with the connecting rod, be equipped with the humidification shower nozzle on the connecting rod, the humidification shower nozzle links to each other with the humidifier, temperature regulating device, the humidifier with the load appearance all links to each other with the power.
Preferably, the length and the width of the soil base layer, the semi-rigid base layer and the surface layer are all 300mm, the soil base layer adopts compacted fine clay, the thickness is 200mm, the semi-rigid base layer adopts cement stabilized macadam, the thickness is 200mm, the connecting part of the semi-rigid base layer and the surface layer is bonded by SBS modified asphalt, and the thickness of the surface layer is 60 mm.
Furthermore, the road structure models are divided into three groups, wherein the surface layer of the first group of road structure models is an SMA-13 asphalt mixture surface layer, the surface layer of the second group of road structure models is an AC-13 asphalt concrete surface layer, and the surface layer of the third group of road structure models is an AM-13 asphalt mixture surface layer.
Preferably, the load instrument is a rut tester, and the temperature control device, the humidifier and the load instrument are all controlled by a controller.
Preferably, the maximum value of the height difference is 10 mm.
The invention also provides an evaluation method of the Top-down type pavement crack model based on the indoor test, which comprises the following steps:
step 1: starting a temperature control device and a humidifier, and preheating a test box to keep the temperature in the test box at 60 ℃ and the humidity at 50%;
step 2: starting the load instrument to enable the load instrument to do reciprocating motion on the road structure model, wherein the wheel load of the load instrument is 0.7MPa, and the rolling frequency is 42 times/min;
and step 3: adjusting the temperature control device according to the cooling amplitude of 3 ℃ per hour, recording the walking times of a load wheel of the load meter when a first crack with the width larger than or equal to 3mm appears on the surface of the surface layer, namely the first crack cracking life n1, and recording the walking times of the load wheel of the load meter when the first crack penetrates through the surface layer to the bottom of the surface layer, namely the first crack cracking life m 1;
and 4, step 4: continuously adjusting the temperature control device (3) with the temperature reduction range of 3 ℃ per hour, wherein the lower limit value of the temperature is-30 ℃, when the lower limit value is reached, heating to 60 ℃ in the proportion of 3 ℃ per hour, and circularly performing the temperature reduction and heating process; sequentially recording the walking times of the load wheel of the load meter when the ith crack with the width larger than or equal to 3mm runs within the time t, namely the cracking life ni of the ith crack, and the walking times of the load wheel of the load meter when the ith crack runs through the surface layer to the bottom of the surface layer, namely the fracture life mi of the ith crack;
and 5: evaluating the crack resistance of the pavement material through a road model crack evaluation index;
step 6: closing the temperature control device and the humidifier, taking out the road structure model after the temperature and the humidity are cooled to room temperature, and repairing cracks with the width of more than or equal to 1cm in a plurality of ways;
and 7: placing the repaired road structure model into a cavity formed by the limiting plate and the bottom plate of the test box again, repeating the steps 1-2, and recording the cracking life n 1' of the first crack of the repaired road structure model;
and 8: the quality of the repairing mode is evaluated based on the first crack cracking life n1 ' of the repaired road structure model, wherein the larger n1 ' indicates the better crack resistance of the road in the repairing mode, and the smaller n1 ' indicates the poorer crack resistance of the road in the repairing mode.
Further, the evaluation indexes of the road model crack comprise a first crack fracture life n1, a first crack fracture life m1, a first crack propagation rate k1 or a crack comprehensive score S;
the larger n1 is, the better the cracking resistance of the material is, and the smaller n1 is, the worse the cracking resistance of the material is;
the larger m1 indicates the better crack resistance of the material, and the smaller m1 indicates the worse crack resistance of the material.
Wherein, the calculation formula of the first crack propagation rate k1 is as follows:
k1＝h1/(m1-n1) (1)
wherein h1 is the thickness of the surface layer, the smaller k1 indicates the better crack resistance of the material, and the larger k1 indicates the worse crack resistance of the material.
Wherein the formulas of the cracking resistance comprehensive score Si and the total score S of the ith crack are respectively as follows:
wherein di represents the width of the ith crack, dmin represents the minimum value of the width of the crack in all the cracks with the width of more than or equal to 3mm, nmax represents the maximum value of the crack service life in all the cracks with the width of more than or equal to 3mm, mmax represents the maximum value of the crack service life in all the cracks with the width of more than or equal to 3mm, omega 1 represents the weight of the width of the crack, omega 2 represents the weight of the service life of the crack, omega 1 and omega 2 are constants, omega 2 is more than omega 1, S represents the comprehensive score of the crack and represents the total score of the crack resistance in one test, k represents the number of the cracks with the width of more than or equal to 3mm within the time t,
the smaller S is, the worse the cracking resistance of the material is, and the larger S is, the better the cracking resistance of the material is.
Preferably, the repairing mode comprises a hot asphalt pouring mode, a crack joint setting mode and a combined mode of hot asphalt pouring and crack joint setting.
The invention has the beneficial effects that:
the application provides a Top-down type pavement crack formation and repair evaluation model based on an indoor test, which simulates the actual stress condition of a road pavement, provides corresponding evaluation indexes, can perform quantitative analysis on crack formation and the existing repair method, and provides certain technical reference for research and development of novel pavement materials and selection of crack repair methods.
1. The road structure model simulates the stress condition of an asphalt pavement in an actual road, and under the action of the load wheel, the semi-rigid base layer with the height difference enables the surface layer to bear shear stress and tensile stress, and meanwhile, the surface layer generates certain tensile stress due to large temperature change, and the state is consistent with the actual stress state.
2. According to the invention, the temperature control device and the humidifying device are additionally arranged in the test model, so that environmental influence factors borne by the road surface in the actual road can be better simulated.
3. The invention provides various evaluation indexes such as the cracking life n, the cracking life m and the crack propagation rate k aiming at the test model, and the quality of the crack resistance can be judged by researching the forming process of different pavement materials TDC under the same condition, thereby providing a certain technical reference for the research and development of novel pavement materials and the selection of a crack repairing mode.
4. The method provides crack repair evaluation indexes aiming at the test model, quantitatively evaluates the crack repair condition, and has certain reference and prior judgment on actual construction.
Drawings
FIG. 1 is a Top-down type pavement crack model diagram based on indoor tests according to the present invention;
FIG. 2 is a schematic illustration of a repair in a fracture model of the present invention.
Detailed Description
The Top-down type pavement crack formation and repair evaluation model based on the indoor test is further described in detail below with reference to the accompanying drawings and the specific implementation method.
As shown in figure 1 of the drawings, in which,
example 1:
the Top-down type pavement crack formation and repair evaluation model based on indoor test comprises a test box 5, wherein a temperature control device 3 is arranged on the side face of the test box 5, a circle of limiting plate 12 is arranged in the test box 5, a road structure model matched in size is placed in a cavity formed by the limiting plate 12 and a bottom plate of the test box 5, the road structure model comprises a soil base layer 8, a semi-rigid base layer 6 and a surface layer 4 which are sequentially arranged from bottom to Top, the semi-rigid base layer 6 gradually sets a height difference from the middle to one end of the semi-rigid base layer, a load instrument 1 is arranged on the surface layer 4, connecting rods 11 are connected to two sides of the test box 5, humidification nozzles 2 are arranged on the connecting rods 11, the humidification nozzles 2 are connected with a humidifier, and the temperature control device 3, the humidifier and the load instrument 1 are all connected with a power supply.
Preferably, the length and the width of the soil base layer 8, the semi-rigid base layer 6 and the surface layer 4 are both 300mm, the soil base layer 8 adopts compacted fine clay, the thickness is 200mm, the semi-rigid base layer 6 adopts cement stabilized macadam, the thickness is 200mm, the semi-rigid base layer 6 and the connecting part of the surface layer 4 adopt SBS modified asphalt to bond, and the thickness of the surface layer 4 is 60 mm.
Furthermore, the road structure models comprise three groups, wherein the surface layer 4 of the first group of road structure models is an SMA-13 asphalt mixture surface layer, the surface layer 4 of the second group of road structure models is an AC-13 asphalt concrete surface layer, and the surface layer 4 of the third group of road structure models is an AM-13 asphalt mixture surface layer.
Preferably, the load instrument 1 is a rut tester, and the temperature control device 3, the humidifier and the load instrument 1 are all controlled by a controller 7. The test instrument adopts a modified asphalt mixture rutting tester, and uses a load wheel thereof for loading, referring to relevant regulations of asphalt mixture rutting tests in road engineering asphalt and asphalt mixture test regulations (JTG E20-2011).
Preferably, the maximum value of the height difference is 10 mm. Because the asphalt pavement can bear certain shear stress when Top-down cracks are formed, the shear stress is caused by unequal heights of roadbed or base layers at two sides of the load, in the road structure model designed by the scheme, the semi-rigid base layer is gradually provided with a height difference from the middle to one end (as shown in the figure, the maximum height difference of the end part can be set to be 10mm according to the roadbed settlement rule and the roadbed pavement construction experience), so that the problems of uneven settlement of the roadbed or uneven thickness of the base layer and the like in the actual road are simulated
The invention has the advantages of complete model, clear and complete condition setting and stress state fitting with the actual condition. As is well known, the TDC is complex in stress state and variable in environmental influence factors, a road surface is subjected to shear stress and tensile stress when being cracked, and stress concentration is generated at the edge of a wheel track. The stress state of a test piece has great influence on the strength of the test piece, in several existing tests, the stress states of the test piece in the shear-resistant test and the tensile test are different from those of a TDC (top dead center) test, but the stress state in the direct stretching, simple shearing or triaxial shearing cannot reflect the influence of stress concentration, and the traditional tensile strength and shear strength test models cannot perfectly evaluate the TDC resistance of the asphalt mixture. The invention develops a novel test model by combining the actual road surface condition, improves the existing instrument and equipment, and maximally simulates the stress state of the road surface in the actual road to research the production process of the TDC and evaluate the crack resistance of the material. Compared with the traditional test method, the test model has the advantages of more reasonable evaluation mode, simpler evaluation index, higher reliability and higher reference value.
TABLE 1 comparison of the different test protocols
Example 2
The invention also provides an evaluation method of the Top-down type pavement crack model based on the indoor test, which comprises the following steps:
step 1: starting the temperature control device 3 and the humidifier, and preheating the test box 5 to ensure that the temperature in the test box 5 is kept at 60 ℃ and the humidity is kept at 50%;
and 2, step: starting the load instrument 1 to enable the load instrument 1 to do reciprocating motion on the road structure model, wherein the wheel load of the load instrument 1 is 0.7MPa, and the rolling frequency is 42 times/min;
and step 3: adjusting the temperature control device 3 according to the cooling amplitude of 3 ℃ per hour, recording the walking times of the load wheel of the load meter 1 when a first crack with the width larger than or equal to 3mm appears on the surface of the surface layer 4, namely the first crack cracking life n1, and recording the walking times of the load wheel of the load meter 1 when the first crack penetrates through the surface layer 4 to the bottom of the surface layer 4, namely the first crack cracking life m 1;
and 4, step 4: continuously adjusting the temperature control device (3) with the temperature reduction range of 3 ℃ per hour, wherein the lower limit value of the temperature is-30 ℃, when the lower limit value is reached, heating to 60 ℃ in the proportion of 3 ℃ per hour, and circularly performing the temperature reduction and heating process; sequentially recording the walking times of the load wheel of the load meter 1 when the ith crack with the width larger than or equal to 3mm is in the time t, namely the cracking life ni of the ith crack, and the walking times of the load wheel of the load meter 1 when the ith crack penetrates through the surface layer 4 to the bottom of the surface layer 4, namely the fracture life mi of the ith crack;
and 5: evaluating the crack resistance of the pavement material through a road model crack evaluation index;
step 6: closing the temperature control device 3 and the humidifier, taking out the road structure model after the temperature and the humidity are cooled to room temperature, and repairing cracks with the width of more than or equal to 1cm in a plurality of ways;
and 7: putting the repaired road structure model into the cavity formed by the limiting plate 12 and the bottom plate of the test box 5 again, repeating the step 1 and the step 2, and recording the cracking life n 1' of the first crack of the repaired road structure model;
and 8: the quality of the repairing mode is evaluated based on the first crack cracking life n1 ' of the repaired road structure model, wherein the larger n1 ' indicates the better crack resistance of the road in the repairing mode, and the smaller n1 ' indicates the poorer crack resistance of the road in the repairing mode.
Further, the evaluation indexes of the road model crack comprise a first crack fracture life n1, a first crack fracture life m1, a first crack propagation rate k1 or a crack comprehensive score S;
the larger n1 is, the better the cracking resistance of the material is, and the smaller n1 is, the worse the cracking resistance of the material is;
the larger m1 indicates the better crack resistance of the material, and the smaller m1 indicates the worse crack resistance of the material.
Wherein, the calculation formula of the first crack propagation rate k1 is as follows:
k1＝h1/(m1-n1) (1)
where h1 is the thickness of face layer 4, a smaller k1 indicates better crack resistance of the material, and a larger k1 indicates worse crack resistance of the material.
The cracking resistance comprehensive score Si and the total score S of the ith crack are respectively expressed by the following formulas:
wherein di represents the width of the ith crack, dmin represents the minimum value of the width of the crack in all the cracks with the width being more than or equal to 3mm, nmax represents the maximum value of the crack life in all the cracks with the width being more than or equal to 3mm, mmax represents the maximum value of the crack life in all the cracks with the width being more than or equal to 3mm, omega 1 represents the weight of the width of the crack, omega 2 represents the weight of the crack life, omega 1 and omega 2 are constants, and omega 2 is more than omega 1, the omega 1 is 0.3, omega 2 is 0.7, S is the comprehensive score of the crack and represents the total score of the crack resistance in one test, and k represents the number of the cracks with the width being more than or equal to 3mm in time t,
the smaller S is, the worse the cracking resistance of the material is, and the larger S is, the better the cracking resistance of the material is.
Preferably, the repairing mode comprises a hot asphalt pouring mode 9, a crack joint setting mode 10 and a combined mode of pouring the hot asphalt 9 and setting the crack joint setting mode 10.
The Top-down type pavement crack model based on the indoor test is used for carrying out the experiment:
1) establishing a road structure model, setting three groups of road structures, wherein the roadbed adopts compacted fine clay, and the thickness of the roadbed is 200 mm; the base layer adopts cement stabilized macadam with the thickness of 200 mm; the surface layer 1 is provided with an SMA-13 asphalt mixture surface layer, the surface layer 2 is provided with an AC-13 asphalt concrete surface layer, and the surface layer 3 is provided with an AM-13 asphalt mixture surface layer, wherein the thickness of the surface layer is 60 mm; all structural layers are 300mm in length and width. The surface layer raw materials are SBS modified asphalt and basalt stone, the connecting part of the surface layer and the base layer is bonded by SBS modified asphalt, and finally the whole structure is placed in a customized template to be fixed.
2) The test equipment adopts an improved rutting tester, the wheel load is 0.7MPa, the rolling frequency is 42 times/min, a temperature control device and a humidifying device are arranged in the tester, the temperature is reduced to-30 ℃ from 60 ℃ at a cooling range of 3 ℃ per hour, and the humidity is controlled to be about 50%.
3) The three road structure models are respectively placed in an instrument for testing, the controller is used for loading, condition control and data acquisition of the three road structures, the frequency of walking of the load wheel is the cracking life n when a first obvious crack appears on the surface of the surface layer (about 3 mm) is observed by adopting a visual method, and the cracking life m is the cracking life m when the crack penetrates through the surface layer to the bottom of the surface layer.
TABLE 2 common pavement surface material TDC resistance test data
The test data show that under the stress state of the same raw material, the same environment and the same and close to the actual road surface, the SMA has higher TDC resistance than the AC and the AM, so that the SMA structure is mostly adopted as the upper layer in the high-grade road surface, not only because the SMA has good surface performance, but also because the framework of the SMA has a compact structure, the SMA has higher crack resistance.
4) The SMA pavement structure with a large-width crack (which can be 1cm) is repaired, and the repairing modes can be divided into three types: pouring hot asphalt, setting crack and joint and combining mode. The three repairing modes are tested under the same condition, and the number of times of walking of the load wheel when obvious cracks appear at the repaired positions of the road surface is the crack service life n 1'.
TABLE 3 common crack repair mode TDC resistance test data (unit: times)
The test data show that the crack repairing effect by adopting the pouring hot asphalt is better than that by setting crack joint, and the combined mode is better than any single repairing mode.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.
Claims (7)
1. A Top-down type pavement crack model evaluation method based on indoor tests is characterized in that a pavement crack model comprises a test box (5), a temperature control device (3) is arranged on the side face of the test box (5), a circle of limiting plates (12) are arranged in the test box (5), a road structure model with matched size is placed in a cavity formed by the limiting plates (12) and a bottom plate of the test box (5), the road structure model comprises a soil base layer (8), a semi-rigid base layer (6) and a surface layer (4) which are sequentially arranged from bottom to Top, the semi-rigid base layer (6) is gradually provided with height difference from the middle to one end of the semi-rigid base layer, a loading instrument (1) is arranged on the surface layer (4), connecting rods (11) are connected to two sides of the test box (5), and humidifying nozzles (2) are arranged on the connecting rods (11), the humidifying spray head (2) is connected with a humidifier, the temperature control device (3), the humidifier and the load instrument (1) are all connected with a power supply,
the road structure model comprises three groups, wherein the surface layer (4) of the first group of road structure model is an SMA-13 asphalt mixture surface layer, the surface layer (4) of the second group of road structure model is an AC-13 asphalt concrete surface layer, the surface layer (4) of the third group of road structure model is an AM-13 asphalt mixture surface layer,
the pavement crack model evaluation method comprises the following steps:
step 1: starting the temperature control device (3) and the humidifier, and preheating the test box (5) to keep the temperature and the humidity in the test box (5) at 60 ℃ and 50%;
step 2: starting the load instrument (1) to enable the load instrument (1) to do reciprocating motion on the road structure model, wherein the wheel load of the load instrument (1) is 0.7MPa, and the rolling frequency is 42 times/min;
and step 3: adjusting the temperature control device (3) according to the cooling amplitude of 3 ℃ per hour, recording the walking times of a load wheel of the load meter (1) when a first crack with the width larger than or equal to 3mm appears on the surface of the surface layer (4), namely the first crack cracking life n1, and recording the walking times of the load wheel of the load meter (1) when the first crack penetrates through the surface layer (4) to the bottom of the surface layer (4), namely the first crack breaking life m 1;
and 4, step 4: continuously adjusting the temperature control device (3) with the temperature reduction range of 3 ℃ per hour, wherein the lower limit value of the temperature is-30 ℃, when the lower limit value is reached, heating to 60 ℃ in the proportion of 3 ℃ per hour, and circularly performing the temperature reduction and heating process;
sequentially recording the walking times of the load wheel of the load instrument (1) when the ith crack with the width larger than or equal to 3mm runs within the time t, namely the cracking life ni of the ith crack, and the walking times of the load wheel of the load instrument (1) when the ith crack runs through the surface layer (4) to the bottom of the surface layer (4), namely the cracking life mi of the ith crack;
and 5: evaluating the crack resistance of the pavement material through a road model crack evaluation index;
step 6: closing the temperature control device (3) and the humidifier, taking out the road structure model when the temperature is cooled to room temperature and the humidity becomes indoor humidity, and repairing cracks with the width being more than or equal to 1cm in a plurality of ways;
and 7: putting the repaired road structure model into a cavity formed by the limiting plate (12) and the bottom plate of the test box (5), repeating the steps 1-2, and recording the cracking life n 1' of the first crack of the repaired road structure model;
and 8: evaluating the quality of a repairing mode based on the first crack cracking life n1 ' of the repaired road structure model, wherein the larger n1 ' indicates the better crack resistance of the road in the repairing mode, and the smaller n1 ' indicates the worse crack resistance of the road in the repairing mode;
the evaluation indexes of the road model crack comprise a first crack service life n1, a first crack service life m1, a first crack propagation rate k1 or a crack comprehensive score S,
the formulas of the cracking resistance comprehensive score Si and the total score S of the ith crack are respectively as follows:
wherein di represents the width of the ith crack, dmin represents the minimum value of the width of the crack in all the cracks with the width of more than or equal to 3mm, ni represents the cracking life of the ith crack, mi represents the cracking life of the ith crack, nmax represents the maximum value of the cracking life of all the cracks with the width of more than or equal to 3mm, mmax represents the maximum value of the cracking life of all the cracks with the width of more than or equal to 3mm, omega 1 represents the weight of the width of the crack, omega 2 represents the weight of the life of the crack, omega 1 and omega 2 are constants, omega 2 is more than omega 1, S is the comprehensive score of the crack and represents the total score of the crack resistance in one test, k represents the number of the cracks with the width of more than or equal to 3mm in time t,
the smaller S is, the worse the cracking resistance of the material is, and the larger S is, the better the cracking resistance of the material is.
2. The indoor test-based Top-down type pavement crack model evaluation method of claim 1, wherein the length and width of the soil base layer (8), the semi-rigid base layer (6) and the surface layer (4) are all 300mm, the soil base layer (8) is made of compacted fine clay and has a thickness of 200mm, the semi-rigid base layer (6) is made of cement-stabilized macadam and has a thickness of 200mm, the connecting part of the semi-rigid base layer (6) and the surface layer (4) is bonded by SBS modified asphalt, and the thickness of the surface layer (4) is 60 mm.
3. The indoor test-based Top-down type pavement crack model evaluation method according to claim 1, characterized in that the loading instrument (1) is a track tester, and the temperature control device (3), the humidifier and the loading instrument (1) are all controlled by a controller (7).
4. The indoor test-based Top-down type pavement crack model evaluation method of claim 1, wherein the maximum value of the height difference is 10 mm.
5. The indoor test-based Top-down type pavement crack model evaluation method of claim 1, wherein the larger n1 indicates the better crack resistance of the material, and the smaller n1 indicates the worse crack resistance of the material;
the larger m1 indicates the better crack resistance of the material, and the smaller m1 indicates the worse crack resistance of the material.
6. The indoor test-based Top-down type pavement crack model evaluation method according to claim 1, wherein the first crack propagation rate k1 is calculated by the following formula:
k1=h1/(m1-n1) （1）
wherein h1 is the thickness of the surface layer (4), the smaller k1 indicates the better crack resistance of the material, and the larger k1 indicates the worse crack resistance of the material.
7. The indoor test-based Top-down type pavement crack model evaluation method according to claim 6, characterized in that the repairing mode comprises hot asphalt pouring (9), crack sealing (10) and a combination mode of hot asphalt pouring (9) and crack sealing (10).
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